<p>A round bilge with a bilge keel structure is a key element which can alleviate the roll motion of ships and floating structures by transferring the roll momentum of a floating body into the kinetic energy of water. This study presents a practical guide to properly designing a bilge radius and bilge keel height of a barge-shaped and tanker-shaped FPSOs. A parametric study to figure out the effect of bilge radius and bilge keel height on the roll damping performance is conducted through a series of numerical roll free decay simulations based on Computational Fluid Dynamics (CFD). The bilge radius is normalized by the half breadth of ship, and the bilge keel height is normalized by the maximum available height that does not exceed the ship breadth. As a result, it is found that the bilge keel height ratio strongly affects the roll damping performance, but the bilge radius ratio does not. Therefore, the equivalent linear and quadratic roll damping coefficients are expressed as functions of bilge keel height ratio. In addition, it is investigated to identify how the roll damping performance of a rectangular section differs from the result of a typical round bilge section with maximum available bilge keel height. The rectangular section is preferred because it is more advantageous from a construction point of view than the attachment of the bilge keel to the round bilge. It is found that the round bilge section with maximum available bilge keel height demonstrates slightly better roll damping performance than the rectangular section, but the difference is not significant. Vortices shed from the knuckle of the rectangular section and bilge keel tip of the round bilge are compared, and it is observed that the vortex contours and strengths of both cases are similar.</p>

Effect of Bilge Radius and Bilge Keel Height on Roll Damping Performance of Floating Structures

Paper Proceedings: https://asmedigitalcollection.asme.org/OMAE/OMAE2021/volume/85116

OMAE 2021

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